Method of making filters.



1,027,754. No Drawing.

HERMANN rnssow, or BLANKENESE, enmrmy.

nn'rnon or MAKING 'rnmnns; I

Specification of Letters Patent.

Application filed March 31,

Patented May 28, 1912.

.1911. Serial No. 618,145.

' To all whom it may concern Be it known that I, HERMANN PASSOW, a subject of the German Emperor, and residing at Wedeler. Chaussee, Blankenese 0. Elbe, Kingdom of Prussia, Germany, have invented certain vnew and useful Improvements in the Method for Making Filters, of

i which the following is a specification.

If an'intimate mlxture of kieselguhr, clay and the like with a suitable flux such as salt, fiuor-spar,'is burned at a high temperature a fritted, porous substance will be producedwhich forms an excellent filtering material, remarkable for its great. strength and its high filtering speed. It mustbe admitted, that it can only partly retain bacteria out of infected water. The reason for this lies in the fact, that in the aforementioned rocess the flux will have such an. effect on t e kieselguhr as tocausethe latter to partly fuse whereby its structure will be changed. The capacity of kieselguhrgnow however, toafford a bacteria proof filtering material, depends as is well known, on the extremely fine structure of the kieselguhr skeletons of microscopical vli'adz'olam'a. If the aforemen tioned burning operation is however carried out at temperatures which will not sufl'ice to completely fuse the filter components, a bacteria proof filtering material will be produced, as the kiselguhr will remain perfectly sound, and this filtering material thus obtamed will be extremely brittle and very sensitive toward outward mechanical and physical influences.

The present invention consists in first pro-. ducing a filtering body by. burning the com-' ponents at a high temperature. Then a further quantity of the compound is ap lied to. or introduced into the thus pro uced lower temperature. By such method plates, sticks and the like can be obtained consisting of layers of a hard and a soft filtering materialwhich, beside its great strength and filtering speed, is. absolutely impermeable toward all kind of rms. The same-result may be obtained if y suitably varying the ratio of the mixture and selecting the flux the sintering points of the raw mixtures are separated so far from each other, that on the same being heated to a given temperabody, whereupon the whole is burned ata ture the one mixture will sinter to a hard clinker like substance under destruction of the kieselguhr structure, while the other will just reach the sintering point. p :7

I claim: 4

1. A method for making filters consisting in a hard filtering bod bein burned 'of a mixture of kieselguhr, c ay an the like with a flux to a sinterln 'point, whereupon a soft filtering layer consisting of the same in d-ients 1s applied to the said. hard filtering body and the whole is again burned at a temperature below the sintering point.

2. A method for making filters consisting in a hard filtering body being burned of a mixture of kieselguhr, clay and the like with a flux to a sintering point, whereupon a soft filtering layer conslstin of the same ingredients is'ap lied to an introduced into the said hard ltering body and the whole is again burned at a temperature below the sintering point. y a I V In testimony whereof I-hereto'aflix. my signature in presence of two witnesses. HERMANN PASSOW.1 Witnesses:

,TH. BASIIEARS Barman, Josnrn YAN DAM. 

